Sanitation in Flood Prone Areas

• Step 1: Evaluating the flooding risk.

Characterize the flood risk by collecting the following data:the area affected by flooding (linked to topography)

• the intensity of flooding (shallow or deep water? slow-moving or fast-moving flood water?)
• the frequency of the flooding event
• the duration of the event.

The aim is to establish a zoning of the territory, distinguishing between areas that are safe for sanitation systems, and those where more or less extensive flood protection measures will be required.

• Step 2: Designing or adapting sanitation systems to withstand flooding

The aim here is to choose sanitation systems which can be operated without interruption, and which do not risk discharging effluent into the environment.
The SPHERE standards recommend “making the excreta containment infrastructure watertight to minimise groundwater contamination” or “building toilets or septic tanks raised”.
Different options should be considered:

• Raising toilets and pits above the highest level of floodwater;
• Reinforcing the walls of latrine pits (lining them with erosion-resistant materials);
• Waterproofing sludge and wastewater containment facilities where they cannot be raised above the maximum flood level;
• Limiting the risk of effluent infiltrating the soil by separating urine from feces (UDDT: Urine-Diverting Dry Toilets);
• Installing non-return valves on septic tanks.

The effectiveness of all of these measures can be enhanced by designing the adaptation measures for wastewater and storm water management together.

Step 3: Taking into account the constraints associated with technical solutions

• Additional construction costs: masonry work on pit walls, raising latrines or tanks;
•  Additional operating costs: lifting wastewater if storage or treatment facilities are raised, more frequent emptying of pits if they are sealed;
•  Adapting technologies to people’s practices: use of urine-diverting toilets, accessibility of elevated toilets for people with reduced mobility, etc.
•  Equipment maintenance capabilities: ability to ensure regular emptying of watertight pits, maintenance of urine-diverting latrines, etc.